Prior-art satellite communications networks use either low-earth orbit (LEO), medium-earth orbit (MEO), or geosynchronous orbit (GEO) satellites to transfer data from a data source to a destination. Such data can include, for example, delay-sensitive data such as voice data communicated during a phone conversation. Voice data is particularly delay-sensitive because long, delay-imposed pauses during oral communications can make communication quality poor. Data requiring transfer through a network also can include non delay-sensitive data such as, for example, system overhead data including: call setup information; TT&C data (telemetry, tracking, and control); routing information; billing information; and short messages (e.g., pages).
LEO satellites are better suited than GEO satellites for communication of delay-sensitive data. Because GEO satellites are located at a substantially greater distance than LEO satellites from the earth-based equipment with which they communicate, significantly longer signal propagation delays are inherent in communications between GEO satellites and earth-based equipment. Because of the delay issues associated with GEO satellites, many prior-art satellite communication networks designed for voice communications use LEO satellites to communicate delay-sensitive data traffic.
The call-handling capacity of a LEO satellite network is inversely proportional to the amount of system overhead data which must be routed through the network. Because system overhead data is routed through the LEO satellites in prior-art systems, the satellites cannot provide as many traffic channels as they would be able to in the absence of such system overhead data.
Because high-capacity systems are highly desirable, what is needed is a method and apparatus which increases the traffic carrying capacity of a satellite network by reducing the effect of transferring system overhead data throughout a system.